Insole



Sept- 2, 1941- M. o. Scl-lun ETAL 2,254,711

INSOLE Filed May 24, 1938 Patented Sept, 2, igdi @25am INSLE Milton 0.Schur and Edward M. Archer, Eerlin,

N. lll., assignors to Brown Company, Berlin, N.. 1&2, a corporation ofMaine Application May 24, 1933, Serial No. 2003i@ (Cl. Sci-44) Cia.

This invention relates to the manufacture of insoles and more especiallyarticialleather insoles comprising a felted iiber base impregnated withrubber or other binder. Artificial leather insoles of this character aregenerally of deiicient scui-resistance especially when, as in the formof welt insoles, they are used in workmens and other shoes and areexposed in the presence of moisture or perspiration directly to the wearor scumng action of the foot.

The insole of the present invention compnses a binder-impregnated feltedfiber base of substantial moisture-transmitting property or vresidualporosity (e. g. a rubber-impregnated paperlike base of substantialresidual vo1d space) and containing a secondary water-resistant binderinfused into the pores or surface port1on of its body only at andimmediately below its foot side or surface, that is, to a depthconstituting only a small fraction of its thickness and in thesubstantial absence of such secondary binder as a coating or film on thefoot side or surface. We have found that such an insole 1s characterizedby the desired high Wet-souilresistant quality on its foot side,part1cularly when the Wet-scuff-proofing material or secondary binder isa thermoplastic rubber derivative, e. g. a rubber halide or hydrohalide,which, besides being highly Water-resistant, evidently bonds oramalgamates well with the rubbercoated or rubber-enveloped fibers of thefelted fiber base. I

While not limited thereto, the present invention will now be describedwith particular reference to the accompanying drawing in terms of theproduction ofv Welt-insole stock having the desired highwet-scui-resistance on its foot side. In the accompanying drawing:

Figure 1 depicts diagrammatically and conventionally the infusion of thewet-scui-proofing material into the superficial pores of the artificialleather stock;

Figure 2 shows the finished stock in the form of a welt-insole blank;

Figure 3 represents a section through the blank on the line 3'3 ofFigure 2; and

Figure 4 is asimilar section after the blank has been channeled todevelop the usual stitchreceiving rib.

The artificial leather stock used for producing the welt-insole hereofmay consist of a threeply structure, all of whose plies consistessentially of a rubber-impregnated felted fiber base. Thus, each plymay be prepared by impregnatformed from reined Wood pulp and/or othersuitable cellulose iiber, with a rubber-latex composition to the desiredsolids or binder content and ,then drying the impregnated web; and theimpregnated plies may then be facially bonded together in superposedrelationship, as with rubber latex or other'suitable binder, into athreeply structure. Such a three-ply structure may, as appears best inFigure 3, comprise afoot-side ply f and a central ply c of approximatelyequal thickness, say, about 0.055", and an outer or external ply e ofabout one-half the thickness of the other plies, say, about 0.027. Boththe foot-side ply f and the external ply e may be impregnated with asimilar rubber latex composition to practically the same solids orbinder content, for instance, to a solids content of about '75%, basedon the dry weight of ber. The central ply c is preferably impregnated,as with a rubber latex composition, to a much higher binder or solidscontent, for instance, to a latex solids or rubber content of about150%, based on the weight of ber. Such comparatively high binder orsolids content in the central ply imparts thereto suflicient toughnessor internal ply adhesion to enable channeling thereof as usual for the prpose of developing, as shown in Figure 4, a stitch-receiving rib r ofrequisite toughness and stitchRholding qualities, especially after theusual gem-duck or fabric (not shown) has been cemented to the externalplyl e and the margins of such fabric are bonded as a reinforcement tothe ribl It might be noted that the resulting composite or three-plysheet is possessed of substantial residual void space andmoisture-transmitting quality such as comport with comfort to the footwhen the sheet is used as insole stock. Y The three-ply'sheet is treatedor superiicially impregnated on its foot-side ply f with the appropriatewetscuii`proong material. Thus, as illustrated in Figure 1, such sheet Smay be progressively unwound from a roll or other accumulation R andpassed over successive applicator rolls I0, I0, each of which may rotatepartially submerged in a bath of the wet-scui-prooiing material andprogressively 'pick up and apply a iilm of such material to thefoot-side surface or ply of the sheet. Specifically, the Wet-scuproongmaterial thus applied to the sheet may consist of a solution ofthermoplastic rubber halide or-hydrohalide (e. g. Pliolite or Tornesite)in a suitable volatile organic solvent, such as gasolene, carbontetrachloride, or the like; and such solution may be, say, about 15% toing an absorptive paper web, for instance, a web 20% solute content andexhibit a thick or syrupy consistency. As the sheet passes into contactwith the applicator rolls I0, it is preferably pressed against suchrolls by adjustable rolls I I, which ride or bear against the sheet andwhose pressure against the sheet is correlated with the concentration oftreating solution, rate of rotation of the applicator rolls, and linearspeed of the sheet so that the desired or requisite amount of solutionis infused locally into the surface pores or portion of the sheet in thesubstantial absence of any lm or coating on the surface. Thesurface-treated or locally Vreimpregnated sheet may then be passedthrough an air-drying chamber, in which it may be exposed while hangingfrom festooning bars to hot air currentsuntil it is dried and ready foraccumulation as a roll I3. In the case of such wet-scuH-proong materialas the thermoplastic rubber derivatives indicated, it is important thatthe temperature of the drying medium is not too high or that the time towhich the sheet is exposed to the hot drying medium is not too long,since such material might be fused and caused to flow unduly from thesurface portion into the body of the sheet, thereby detracting from thesurface-proofing effect desired. It has been found that the desiredretention or localization of such material at the surface portion of thesheet during drying may be realized by using as the drying medium airheated to a temperature downwards of about 212 F., say, about 180 F.

In actual practice, the desired proofing of the foot side of thewelt-insole stock may be realized with only about 2 to 6 grams of thewet-souffproofing rubber derivative per square foot of stock, providedthat virtually all of such proofing material is sunk or infusedimmediately below the surface, insomuch that there is no sensiblecoating or film of such material left on the surface and the fibroustexture of the surface is apparent. Through such a surface proofingtreatment, it was possible so to improve the weltinsoie stock that,whereas the untreated weltinsole stock quickly deteriorated and becameunsightly on its foot side under drastic conditions of use, namely, in aworkmans shoe, the treated welt-insole hereof used under the sameconditions gave no sign of failure after months of use. It might benoted that the surface proofing treatment hereof, although increasingthe surface-tightness of the insole, does not destroy its porosity.Thus, a number of Gurley airporosity tests made simply on the foot-sideply after the surface proofing treatment or impregnation hereof showedvalues ranging from 75 to 250 seconds for 100 cc. of air forced ortransmitted through an area of 1" diameter, whereas similar tests onsuch ply before the surface treatment or impregnation hereof showed muchlower values, namely, from less than l second to 10 seconds. Theseparticular values were secured with a foot-side ply pf the particularcharacteristics of thickness and rubber latex impregnant content alreadyindicated for the foot-side ply f. In many cases, the Gurley test on thebonded or plied-up and surface-treated or scuff-proofed insole producthereof (i. e. after the seuil-proofing treatment on the foot side) runsunder 300 seconds, indicating that the residual voids in the plies ofsuch product may inter-communicate'to a very great extent.

It is vitally important that the wet-scuf-proofing material be sunk orinfused practically entirely and locally into the pores of the insole atand immediately below the foot side r surface in order to realizesatisfactory results. When such material is deposited largely or to asubstantial extent as an external coating or film on the surface of thefoot-side ply, it tends to crack and check during wear and also to burnthe foot on account of its practically complete destruction of theporosity or breathing quality of the insole; and perspiration stains thesurface cracks and checks and quickly renders the insole unsightly. Bysinking or infusing the wet-scuif-proong material to the proper degreelocally into the surface pores or portion of the foot-side ply, it ispossible desirably to retain the surface porosity or breathing qualityof the insole and thus to avoid burning of the feet while at the sametime realizing the marked surface-reinforcing effect or highwet-scuff-resistance with but very little usage of such material, sincesuch material is not dissipated throughout the body of the insole but,rather, is

concentrated to only a limited depth in the insole, namely, a depthconstituting only a very small fraction of the thickness of thebinderimpregnated insole body or fibrous base.

The insoles to which the wet-scuff-proofing treatment hereof is appliedare broadly of the binder-impregnated felted fiber or paper base varietyand are possessed of substantial void space and moisture-transmittingquality. It is possible to use other than rubber as the primary binderor impregnant throughout the base, for instance, rubber 'latexcompositions or compounds containing such other binders as casein,viscose, starch, or the like, or to use essentially a non-rubber binder,for instance, a starch binder such as is disclosed in Schur et al.application Serial No. 207,308, filed May 11, 1938. Insoles or insolestock embodying the present invention may be of various thicknesses andbe of single-ply or multi-ply structure and of various primary bindercontents. It is usually preferable, however, to build up the insolestock to the desired thickness from two or more binderimpregnated feltedfibrous plies of similar or dissimilar contents of binder, such asrubber. Indeed, in the case of a welt-insole, it is, as alreadyindicated, usually advantageous to build up the insole structure or bodyfrom at least three binder-impregnated plies, the central ply of whichis of markedly higher binder content than the surface plies and theouter ply of which is thinner than the foot-side ply. However, thewelt-insole might be made up of two plies with a foot-side ply ofmarkedly lower rubber content than the outer or under ply, for instance,with a foot-side ply of a rubber content of about 60% to 90%, based onthe weight of fiber, and an outer or under ply of a rubber content ofabout to 200%, based on the weight of fiber. A welt-insole structurethus produced and, in accordance with the present invention,scuff-proofed on its foot side has been found to be eminentlysatisfactory for use in lieu of a much more expensive leatherwelt-insole, especially when halogenated thermoplastic rubberderivatives constitute the wet-souff-Proong medium in combination with arubber primary binder in the felted fibrous base or insole body.

We claim:

1. An insole consisting essentially of a porous, binder-impregnated,felted fiber base whose foot-side portion contains a halogenated,thermoplastic rubber derivative in the amount of about two to six gramsper square foot practically completely confined to the pores at thefoot-side surface and to pores extending from such surface to a depthconstituting only a small fraction of the thickness of said base, saidfootside portion, despite its content of said derivative, beingpossessed of appreciable residual porosity, as determined by itscapability of transmitting an appreciable amount of air under Gurleytest.

2. 'An insole consisting essentially of a porous, rubber-impregnated,felted iiber base whose foot-side portion contains a halogenatedthermoplastic rubber derivative in the amount of about two to six gramsper square foot confined practically completely to the pores at thefootside surface and to pores extending from such 15 surface to a depthconstituting only a small fraction of the thickness of said base, saidfoot-side portion, despite its content of said derivative, beingpossessed of appreciable residual porosity, as determined by itscapability of transmitting an appreciable amount of air under Gurleytest.

3. An insole consisting essentially of a porous rubber-impregnated,felted fiber base containingl as an additional impregnant in itsfoot-side portion a thermoplastic rubber derivative practically 2.

completely concentrated in and immediately below the surface pores ofthe foot-side, said footside portion, despite its content of saidderivative, being possessed of appreciable residual porosity, asdetermined by its capability of transmitting an appreciable amount ofair under Gur--Y- ley test.

4. An insole consisting essentially of a porous, rubber-impregnated,felted fiber base containing as an additional impregnant in itsfoot-side portion a halogenated thermoplastic rubber derivative in theamount of about two to six grams per square foot practically completelyconcentrated in and immediately below the surface pores of thefoot-side, said foot-side portion, despite its content of saidderivative, being possessed of appreciable residual porosity, asdetermined by its capability of transmitting an appreciable amount ofair under Gurley test.

5. An insole consisting essentially of a porous, binder-impregnated,felted ber base containing as an additional impregnant in its foot-sideportion a thermoplastic rubber derivative practically completelyconcentrated in and immediately below the surface pores of thefoot-side, said footside portion, despite its content of saidderivative, being possessed of appreciable residual porosity, asdetermined by its capability of transmitting an appreciable amount ofair under Gurley test.

MILTON O. SCHUR. EDWARD M. ARCHER.

